The invention relates to a corporation stop of the type adapted to be installed in the sidewall of a fluid bearing conduit to form a junction or branch and, specifically, to such a stop that is adapted for installation within a lined conduit using standard drilling and tapping machines.
A variety of circumstances exist in which it is desirable to form a junction or branch line from a main, fluid carrying conduit. For instance, in the municipal area, it is often necessary to install a branch line into a water main, gas main or sewer main. A similar need exists in other industries, such as in the chemical pipeline industries.
In the municipal area, many water mains were constructed years ago and the wall structures are now badly eroded or collapsing. In order to repair such damage, it has been proposed to insert a liner within these lines to provide a new water-impervious wall to the system. There are various different methods available in the industry for inserting synthetic liners within existing conduits, such as the cured-in-place, fold-and-form and diameter reduction methods, each of which inserts a liner from one end of the conduit to the other. However, the wall of the line is usually not continuous since branch lines intersect the main conduit at various entry ports to allow the free flow of fluid from the main to the branch line. In the case of existing and newly formed entry ports, it is desirable to utilize a corporation stop at the junction to control the fluid on either a temporary or permanent basis.
Although a variety of corporation stops are known in the prior art, all suffer from various deficiencies. Many of the prior art assemblies are complicated in design and are time consuming to install. In many cases, it was not possible to install the stop on a "live" line that was carrying fluid under pressure. Although standardized machinery has been developed for installing corporation stops in conduits carrying fluid under pressure, such as the B-101 drilling and tapping machines manufactured by Mueller Co., this machinery is not well suited for use with a conduit that has been lined or rehabilitation with a synthetic liner.
The prior art corporation stop assembly that is specifically designed for installation in a conduit that is lined with a synthetic liner is disclosed in U.S. Pat. No. 5,199,145 (McMillan et al.). The corporation stop assembly disclosed therein has a flexible sleeve member and a threaded stem with an enlarged head portion, and is installed into the lined conduit by way of a clamp nut that engages the neck portion of the threaded stem for forcibly moving the lower end of the sleeve member over the head portion of the stem to expand the lower end of the sleeve member and form an internal seal with an opening in the conduit. The McMillan patent also discloses a specific apparatus to be used for installing that corporation stop in a live, pre-lined conduit carrying fluid under pressure.
While this corporation stop is effective for use in lined conduits carrying therein fluid under pressure, the apparatus shown in the McMillan patent for installing the corporation stop in a lined conduit is fairly large and unwieldy and may not be suitable for situations in which the space available along the conduit adjacent the spot for installation of the corporation stop is less than the amount of space physically required by the disclosed installation apparatus. Furthermore, the McMillan patent shows no way in which the corporation stop disclosed therein can be installed using standard drilling and tapping equipment, such as the Mueller B-101 machine for drilling, tapping and installing corporation stops in unlined conduits, and others manufactured by ALH and Wask, which are well known to those skilled in the art.